In this study, crude petroleum benzene, chloroform, methanol and water extracts of six selected vegetables namely, garlic chives (Allium tuberosum), celery (Apium graveolens (L.)), sweet potato leaves (Ipomoea batatas (L.)), curry leaves (Murraya koenigii (L.)), winged beans (Psophocarpus tetragonolobus) and sweet leaves (Sauropus androgynus) were tested for antioxidant activities using three bioassays namely 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, reducing power assay and metal chelating assay. Overall, among the 24 crude extracts tested, petroleum benzene and chloroform extract of Murraya koenigii (L.) showed higher free radical scavenging activities (IC50 = 0.02 mg/mL and 0.0225 mg/mL, respectively) when compared to ascorbic acid (IC50 = 0.00375 mg/mL) and strong reducing powers with absorbance value of 1.208 ± 0.006 and 1.833 ± 0.003 when compared to butylated hydroxyanisole with absorbance value of 2.625 ± 0.004 at the highest concentration tested, 1 mg/mL in both DPPH and reducing power assay, respectively. In metal chelating assay, methanol, petroleum benzene and chloroform extracts of Murraya koenigii (L.) showed moderate metal chelating activities of 88.60 ± 0.02%, 78.30 ± 0.23% and 73.61 ± 0.22%, respectively, at 1 mg/mL when compared to ethylenediaminetetraacetic acid which is 98.63 ± 0.13%. These findings suggested the important significance of Murraya koenigii (L.) consumption in prevention of diseases.
Tinospora crispa and Tabernaemontana corymbosa have been used traditionally to treat fever, diabetes, rheumatism and sinusitis. The objective of this study was to evaluate the antioxidant activity of Tinospora crispa and Tabernaemontana corymbosa. The presence of apigenin and magnoflorine was detected using LCMS/MS in Tinospora crispa (Patawali) whereas appararicine, voafinine, conodusarine, conodurine, voacamine and voacangine were detected in Tabernaemontana corymbosa (Susur kelapa) methanol extract. The stem extract of Tinospora crispa showed high antioxidant activity in the following order: DPPH radical scavenging, reducing power and metal chelating assay (98.8%, 0.957, 81.97%) than Tabernaemontana corymbosa of leaves (90.04%, 0.652, 69.64%), stem (82.78%, 0.819, 36.70%) and root extracts (63.25%, 0.469, 51.56%), respectively. The high antioxidant activity in the stem extract of Tinospora crispa is due to the presence of apigenin and magnoflorine. The high antioxidant activity in Tabernaemontana corymbosa extract is due to its high phenol contents. There were significant linear positive correlation (r=0.788, p<0.001, r2=0.621) between the total phenolic content and DPPH free radical scavenging assay in the crude extracts of Tinospora crispa and Tabernaemontana corymbosa. Meanwhile, a significant moderate positive correlation was observed between the total phenolic content and ferric reducing power assay (r= 0.556, p<0.05, r2= 0.309). However, there was no significant difference in the correlation coefficient of total phenolic content and metal chelating assay.